1. Field of the Invention
The present invention generally relates to a device and an image adjustment method and, more particularly, to a device and an image adjustment method by simultaneously adjusting the luminance and the chrominance of an image.
2. Description of the Prior Art
To date, there exist many conventional approaches to image color enhancement based on the information distribution of luminance signals in a frame histogram, which is a relationship diagram with the amount of corresponding luminance values in an image.
Please refer to FIG. 1, which is a schematic circuit diagram for image contrast enhancement with respect to using a statistic histogram in the prior art. In FIG. 1, the input luminance value can be figured out by a statistic histogram extracting device 110 after an input luminance signal Yin is fed into the statistic histogram extracting device 110. Moreover, luminance distribution information 115 corresponding to the luminance value can be obtained in light of the statistic histogram generated by the statistic histogram extracting device 110. Due to the luminance distribution information 115, the luminance curve (the relationship curve between luminance and luminance value) device 120 outputs the luminance curve of a new luminance signal Yout.
Therefore, among the input luminance signal Yin and the input chrominance signal (Cbin, Crin) of every frame in an image, only the input luminance signal Yin is transformed into an output luminance signal Yout by means of the statistic histogram extracting device 110 and the luminance curve device 120.
In the prior art method, even though image contrast is improved, only the luminance is changed but the chrominance is still the same, which leads to the loss of image saturation under some situations. Therefore, blurs occur near the boundaries of picture patterns.
A conventional method for preventing the aforementioned drawback is using a statistic histogram extracting device to obtain an output luminance signal and a compensating function to compensate chrominance signals. Please refer to FIG. 2, which is another conventional circuit diagram for image contrast enhancement. In FIG. 2, not only the input luminance signal Yin passes through a statistic histogram extracting device 210 and a luminance curve device 220 as to obtain an output luminance signal Yout, but also the input chrominance signal (Cbin, Crin) passes through a color compensating device 230 as to obtain an output chrominance signal (Cbout, Crout) according to the input luminance signal Yin and the output luminance signal Yout. The input chrominance signal (Cbin, Crin) of every picture pattern in an image can be compensated as to overcome the blurs near the boundaries of picture patterns using the compensating function of the color compensating device 230.
However, in the prior art method, the image luminance may not meet the viewer's requirements. Therefore, there is a need to provide a method and an image adjustment device by simultaneously adjusting the luminance and the chrominance of an image such that the image luminance and image chrominance can meet the viewer's requirements.